"A figure of 60% of all coffee species threatened with extinction is extremely high, especially when you compare this to a global estimate of 22% for plants," said Dr Eimear Nic Lughadha, who leads Kew's planet assessment unit.

"Some of the coffee species assessed have not been seen in the wild for more than 100 years, and it is possible that some may already be extinct."

Arabica coffee makes up 60% of the world's multibillion pound coffee industry. Scientists at Kew worked with Ethiopian collaborators to reveal the enormous threat posed to these plants by climate change.

As global temperatures soar, the researchers estimate natural populations of arabica are likely to halve by the end of the century.

Coffee farmers growing this species — as well as robusta coffee that makes up the other 40% — have reported their crops being affected by longer dry seasons and the spread of pests.

The scientists emphasised the role that wild coffee could have in ensuring the coffee sector survives in a changing world.

"Among the coffee species threatened with extinction are those that have potential to be used to breed and develop the coffees of the future, including those resistant to disease and capable of withstanding worsening climatic conditions," said Dr Aaron Davis, head of coffee research at Kew.

The team called for emergency action to protect coffee species both in the wild and in special facilities like seed banks.

As it stands, less than half of strains are held in storage, and over a quarter fall outside the range of any special protected zones.